school energy&environment

Cluster and supercluster of galaxies

The structure of our Universe seems like a kind of sponge. As a matter of fact, the measurement of the placements of thousands of galaxies showed us that they are not equally arranged. On large-scale, the Universe is composed by groups of galaxies, called clusters, creating all together giant and flat thickenings. They are divided by immense and empty regions.
Moreover, many galaxy clusters are involved in overall motions towards other large clusters, called attractors, because of their gravitational force.
The birthplace of this large-scale structure seems to be hidden in very small unhomogenities in the initial matter distribution. After the Big Bang, on a chronological time of billions of years, the gravitational forces would have condensed the matter, creating at first the galaxies, then clusters and superclusters, and in the end the larger structures, like the attractors.
Before 1989, scientists supposed that supercluster represented the largest structures in the whole Universe, equally placed everywhere in the Universe. Instead, in 1989, Margaret Geller and John Huchra discovered a real wall of galaxies, extended for more than 500 millions of light years, large 200 millions, with a thickness of 15 millions. They called it “Great Wall”.